Integrated circuits are used in many portable electronic products, such as cell phones, portable computers, voice recorders, etc. as well as in many larger electronic systems, such as cars, planes, industrial control systems, etc. Integrated circuits may include a combination of active devices, passive devices and their interconnections. In order to electrically connect the integrated circuit components to a point external of it, bond pad structures are provided.
The schematic cross-section of FIG. 1 illustrates a known integrated circuit system 100 comprising a substrate 101 having a top metal layer 112 embedded within an interlayer dielectric 110. Attached to a lower surface of the top metal layer 112 is a via 114 which may be connected to an underlying metal layer or circuit components (not shown). A bond pad 120 is formed at an upper surface of the top metal layer 112. The bond pad is conductive and may comprise metals such as aluminum-based alloys (such as Al—Cu or Al—Cu—Si). A passivation layer 140 is formed over the interlayer dielectric 110 and the bond pad 120, with an opening created in the passivation layer 140 so that an upper surface portion of the bond pad 120 is exposed. As illustrated in FIG. 1, a ball bond 160 is formed in contact with the exposed portion of the bond pad. The ball bond 160 has a wire bond 162 attached thereto for connecting the bond pad 120 and hence integrated circuit to a location external of it. The location external of the integrated circuit may include packaging leads, a circuit board or another integrated circuit.
A problem often encountered in the fabrication of integrated circuits is bond pad corrosion which is the depletion of materials used in the bond pad. This phenomenon is undesirable because it results in the formation of pits or pinholes at the upper surface of the bond pad which can affect the adhesion reliability of subsequent bonding contacts such as ball bonds to the bond pad. Therefore, fabrication processes that can mitigate the problem of bond pad corrosion are desirable.